Found a partial solution, but it’s VERY hacky and pretty buggy. Basically used the scale tool to make one end of a cutaway smaller.
This is the piece I want to extrude (ignore the other ones behind it). The corner with the gizmo is where the fillet should be zero, and the far side is 3mm.
I made a 6mm square with a 6mm circle in it, so one of the corners is the overall fillet that I want to cut (the same as what you’d get from just filleting an edge R3mm, I could’ve done that and subtracted a copy I suppose)
I then opened up the scale tool and moved the pivot to the outer corner
Scaling to zero doesn’t work, but I found that 0.001 does. It collapses to a point. If you highlight it and select fully included items over the point, with Faces Only selected, nothing gets selected.
Behold, a pointy fillet. I’m guessing the engine is doing some floating-point rounding for the very, very small size.
I moved it over to the block I wanted to cut from
Subtracted it from the block
And, done. At a glance it seems to work, but if you look closely you can see there’s some weird glitchiness going on with the shading.
Front view, with the artifacting a bit more apparent.
Side view, VERY apparent
But hey, backside looks good
The shading looks pretty wonky, but honestly the shape itself is wonky - it makes sense it’d be sharp at the far corner and smooth at the other. But in theory it should look smooth almost immediately after the corner, since it instantly becomes a fillet. The gradient would be small but smooth, this looks like what you’d get from an alpha fade from full gradient shadow to full sharp shadow.
I don’t care about the shading, but the fact that it looks funky implies the engine really doesn’t like what’s going on. Honestly I hate using the Scale tool, it’s so arbitrary where designs have to be so precise.
If there’s a less hacky way to achieve this, please let me know! Cheers